Check Headlight System

Trouble symptom:

Headlight does not illuminate, or headlight is weak.

Wiring diagram:

Headlight system Ref. to WIRING SYSTEM>HEADLIGHT SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

NOTE: Operate the appropriate switch according to the inspection condition.

CHECK HEADLIGHT ILLUMINATION .
1. Turn the ignition switch to ON.
2. Turn the lighting switch to the switch 2 (HEAD) position and switch UP (HI) position.
  Does the headlight (low beam and high beam) come on?
Yes: The headlight system is normal.

No: Go to 2.
CHECK DTC .
1. Turn the ignition switch to ON.
2. Turn the lighting switch to the switch 2 (HEAD) position and switch UP (HI) position.
3. Read the DTC of [Front Relay Control Module] using the Subaru Select Monitor. Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
Are any DTCs displayed?

Yes: Perform the diagnosis according to the displayed DTC. Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST .

No: Go to 3.
CHECK POWER SUPPLY .
Display the data of [BATT Voltage (Control)], [BATT Voltage (BACKUP)] and [IGN Voltage] using Subaru Select Monitor. Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DATA MONITOR .

Is the voltage 9 - 16 V?

Yes: Go to 4.

No: Check the front relay control module and replace it if defective.

Inspection: Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .

Replacement: Ref. to BODY CONTROL/COMMUNICATION SYSTEM>FRONT RELAY CONTROL MODULE .
PERFORM ACTIVE TEST .
Using the Subaru Select Monitor, check the following items in the [Active Test] of [Front Relay Control Module]. Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>ACTIVE TEST .

NOTE: Check the items where illumination did not occur in step 1).
- [Lighting Low RH Output]
- [Lighting Low LH Output]
- [Lighting High RH Output]
- [Lighting High LH Output]
Does the light illuminate?

Yes: Go to 9.

No: Go to 5.
CHECK HEADLIGHT POWER SUPPLY CIRCUIT .
1. Turn the ignition switch to OFF.
2. Disconnect the front relay control module connector.
3. Measure the voltage between front relay control module connector and chassis ground.
  Connector & terminal
  
  Headlight RH
  
  (B68) No. 1 (+) - Chassis ground (-):
  
  Headlight LH
  
  (B69) No. 6 (+) - Chassis ground (-):
Is the voltage 9 - 16 V?

Yes: Go to 6.

No: Check the harness of the fuse, connector and power supply circuit. If there are no problems, replace the front relay control module. Ref. to BODY CONTROL/COMMUNICATION SYSTEM>FRONT RELAY CONTROL MODULE .
CHECK HARNESS .
1. Disconnect the connector of the light which did not illuminate.
2. Check the harness between the front relay control module and the headlight.
  Connector & terminal
  - Except for WILDERNESS model
    Headlight RH (low beam)
    
    (B68) No. 2 - (B121) No. 4:
    
    (B68) No. 2 - (B121) No. 10:
    
    Headlight RH (high beam)
    
    (B69) No. 2 - (B121) No. 6:
    
    Headlight LH (low beam)
    
    (B69) No. 8 - (B122) No. 4:
    
    (B69) No. 8 - (B122) No. 10:
    
    Headlight LH (high beam)
    
    (B69) No. 7 - (B122) No. 6:
  - WILDERNESS model
    Headlight RH (low beam)
    
    (B68) No. 2 - (B121) No. 10:
    
    Headlight RH (high beam)
    
    (B69) No. 2 - (B121) No. 6:
    
    Headlight LH (low beam)
    
    (B69) No. 8 - (B122) No. 10:
    
    Headlight LH (high beam)
    
    (B69) No. 7 - (B122) No. 6:
Is harness normal?

Yes: Go to 7.

No: Repair or replace the harness.
CHECK HEADLIGHT .
Apply battery voltage between headlight unit connector terminals.
- Make sure that the high beam illuminates because the high beam shares the same lighting body with the low beam and they are alternatively lit by switching .
- When applying battery voltage, do not mix up the positive (+) side and the negative (-) side. Incorrect polarity connection may cause internal LED damage .
  Connector & terminal
  - If the low beam does not illuminate
    Headlight RH
    
    (B121) No. 10 (+) - (B121) No. 14 (-):
    
    Headlight LH
    
    (B122) No. 10 (+) - (B122) No. 14 (-):
  - If the high beam does not illuminate
    Headlight RH
    
    (B121) No. 10 and (B121) No. 6 (+) - (B121) No. 14 (-):
    
    Headlight LH
    
    (B122) No. 10 and (B122) No. 6 (+) - (B122) No. 14 (-):
Does the headlight (low beam and high beam) come on at normal brightness?

Yes: Go to 8.

No: Replace the headlight assembly. Ref. to LIGHTING SYSTEM>HEADLIGHT ASSEMBLY .
CHECK HARNESS .
Check the harness between the headlight connector and the chassis ground.

Connector & terminal

Headlight RH

(B121) No. 14 - Chassis ground:

Headlight LH

(B122) No. 14 - Chassis ground:

Is harness normal?

Yes: Check the front relay control module and replace it if defective.
- Inspection: Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .
- Replacement: Ref. to BODY CONTROL/COMMUNICATION SYSTEM>FRONT RELAY CONTROL MODULE .
No: Repair or replace the harness.
CHECK CURRENT DATA .
1. Turn the ignition switch to ON.
2. Display the data of [Lighting II Switch Input] and [Dimmer Hi Switch Input] using Subaru
Select Monitor. Ref. to BODY CONTROL (DIAGNOSTICS)>DATA MONITOR .

Does the display change between [OFF] ←→ [ON] when the lighting switch is moved to the switch 2 (HEAD) and switch UP (HI) positions?

Yes: Go to 10.

No: Check the combination switch or harness for open circuit.
CHECK CURRENT DATA .
1. Turn the ignition switch to ON.
2. Display the data of [Lighting Low Request] and [Lighting High Request] using Subaru Select Monitor. Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DATA MONITOR .
Does the display change to [ON] when turning the lighting switch to the switch 2 (HEAD) position and switch UP (HI) position?

Yes: Replace the front relay control module. Ref. to BODY CONTROL/COMMUNICATION SYSTEM>FRONT RELAY CONTROL MODULE .

No: Replace the body integrated unit. Ref. to BODY CONTROL/COMMUNICATION SYSTEM>BODY INTEGRATED UNIT .